The present invention relates in general to a variable displacement compressor piston, and, more particularly, to a variable displacement compressor piston having a hollow piston body axially aligned and integral with an actuator rod.
Variable displacement compressor pistons are used in a variety of applications including, for example, compressors used in automobile air conditioning systems. One method of producing such a piston involves forging a solid piston body with an accompanying integral actuator arm. A piston ring is added to the solid piston body to maintain sufficient air compression as the piston slides in a bore in a reciprocal fashion during compressor operation. The two components of such a piston must be manufactured separately and be later assembled thereby increasing production time and cost. Further, the solid piston body has a relatively large mass which increases reciprocating inertia in the system, and thus, reduces efficiency of the piston.
Another method of producing a variable displacement piston involves manufacturing a hollow piston body, typically by extrusion, and welding the hollow piston body to an actuator arm, which is typically formed by forging. The outer surface of the hollow piston body is machined along its length such that a piston ring is not required to maintain sufficient air compression during piston strokes. However, two parts still must be manufactured and assembled. Further, the piston body and actuator arm require machining to produce an appropriate surface at the joint where the two parts are welded together. The machining operation requires that the piston body and the actuator arm be precisely aligned during welding which is difficult. Improper alignment, due to lack of straightness, concentricity, perpendicularity and runout can result in unusable pistons once the machining operation is performed.
Accordingly, there is a need for a process of producing variable displacement compressor pistons which can be machined with little or no possibility of rendering the pistons unusable due to the machining operations. Preferably, such a process would produce pistons having relatively little mass and requiring no piston rings. Further, to improve manufacturing efficiency and accordingly expense, the process should require fewer and/or more simplified manufacturing steps.